Dried up polish can be very unattractive. It is also a hardened substance that can cause surface damage when rubbed over the paintwork. Although the detailer should have removed this, it can be encountered on some jobs. Dried up wax residue can generally be approached in the same way.
Soak while washing
When the residue is not very old, it will be soft enough to be washed off. The advantage is that the shampoo will help to lubricate the particles, making it much less likely to make any surface imperfections. A downside is that it might require some time to fully soak the residue off. Seeing as polish contains oils, it is recommended to follow up with or a similar product to remove the oily residue.
Scrape the residue off
A plastic razor can help to remove big parts of residue. Although the plastic razor won’t cause any imperfections, the polish particles can still have qualities while rubbing around. This method could work on older bits or dried up polish.
In some cases the polish covers a very sensitive area, and soaking with shampoo won’t work. In these cases it can help to soak a cloth in or similar, and cover the blob of polish with the cloth. The wet cloth will slowly soften the polish particle. When it is soft enough, it can be wiped off with a washmitt and some shampoo or a soft microfiber towel.